A semiconductor device, e.g., a transistor is ordinarily constituted of a gate electrode, a gate insulating film, a source electrode, a drain electrode, a passivation film (protective film) and so on formed on a substrate. As the substrate (object to be processed), a silicon wafer, a glass substrate or the like is used. As the electrodes, a metal such as Al, a polysilicon or the like is used. As an interlayer insulating member comprising the passivation film, silicon nitride, silicon oxide, silicon carbide or the like is used.
Silicon oxide film is ordinarily used as the above-mentioned gate insulating film. With the reduction in device size and with the improvements in characteristics achieved by increasing the operating speed for example, studies have been made of using as the gate insulating film a silicon nitride film whose dielectric constant (7.9) is larger than that (3.9) of silicon oxide film, hafiiia (HfO2), silicate and aluminate of this (a mixture of Hf (hafnium)-Si—O and Hf—Al—O) and materials obtained by doping these with nitrogen (varying in dielectric constant depending on the composition).
Patent Document 1 discloses a thin film forming apparatus in which a plasma CVD device in line form formed of a plasma generating section in line form and an introduction section through which a reaction gas is introduced, an annealing section in which a thin film formed by this plasma CVD is annealed with light in line form and a plasma processing device in line form for processing the surface of the annealed thin film with plasma are disposed in series, and which is capable of eliminating impurities in the amorphous silicon surface and obtaining a good device with improved reproducibility.
Silicon nitride film formed by an ordinary film formation method such as a plasma CVD or CVD, however, has many electrons or hole traps existing therein and is, therefore, disadvantageously low in reliability. There is also a problem that, while there is a need to form a uniform silicon nitride film having a thickness of several nanometers with stability, it is difficult to form a film uniform in thickness with satisfactory reproducibility.
The applicant of the present invention already filed a patent application of a silicon wafer nitriding method and apparatus for forming a silicon nitride film on a silicon wafer surface so that electrons or hole traps in the film are reduced (see Patent Document 2).
The following are examples of documents relating to the above-described arts.
1) JP Patent Publication (Kokai) No. 2002-100578A
2) JP Patent Publication (Kokai) No. 2002-324795A